javascript - Any way to modify Jasmine spies based on arguments?

Question

I have a function I'd like to test which calls an external API method twice, using different parameters. I'd like to mock this external API out with a Jasmine spy, and return different things based on the parameters. Is there any way to do this in Jasmine? The best I can come up with is a hack using andCallFake:

var functionToTest = function() {
  var userName = externalApi.get('abc');
  var userId = externalApi.get('123');
};


describe('my fn', function() {
  it('gets user name and ID', function() {
    spyOn(externalApi, 'get').andCallFake(function(myParam) {
      if (myParam == 'abc') {
        return 'Jane';
      } else if (myParam == '123') {
        return 98765;
      }
    });
  });
});

Answer 1

In Jasmine versions 3.0 and above you can use withArgs

describe('my fn', function() {
  it('gets user name and ID', function() {
    spyOn(externalApi, 'get')
      .withArgs('abc').and.returnValue('Jane')
      .withArgs('123').and.returnValue(98765);
  });
});

For Jasmine versions earlier than 3.0 callFake is the right way to go, but you can simplify it using an object to hold the return values

describe('my fn', function() {
  var params = {
    'abc': 'Jane', 
    '123': 98765
  }

  it('gets user name and ID', function() {
    spyOn(externalApi, 'get').and.callFake(function(myParam) {
     return params[myParam]
    });
  });
});

Depending on the version of Jasmine, the syntax is slightly different:

• 1.3.1: .andCallFake(fn)
• 2.0: .and.callFake(fn)

Resources:

• withArgs docs
• callFake docs
• andCallFake vs and.callFake